The embodiments disclosed herein relate to camera modules. Particularly, the embodiments disclosed herein relate to a continuous autofocus system within camera modules.
Camera modules are becoming increasingly popular within portable electronics. Not only are camera modules within stand-alone cameras, but they are in essentially all smartphones, tablets and PC computers. Camera modules include auto focus systems such that a particular camera module can focus on a specific object within a captured image.
Current autofocus systems require a time interval whereby the camera module is held stationary such that the camera can acquire an object and determine the correct focus configuration. This time interval is inefficient as current autofocus systems require 125 ms or more to find the best focus.
FIG. 1 depicts an exemplary prior art autofocus system 100 within a camera module. FIG. 2 depicts an exemplary prior art autofocus position calculation diagram utilized by autofocus system 100, of FIG. 1. FIGS. 1-2 are best viewed together with the following description.
Autofocus system 100 includes an image generation portion 102 having a lens 104 for capturing, via image sensor 106, and an autofocus voice coil motor (AF VCM) 108 for translating lens 104 to a focus position along a focus translation stage (not shown). AF VCM 108 is controlled via driver circuit 110. Driver circuit 110 is configured by image signal processor (ISP) 112. ISP 112 receives data, via an inter-integrated circuit (I2C) Bus from image sensor 106 as described below with reference to FIG. 2.
ISP 112 controls AF VCM 108, via driver circuit 110, such that lens 104 is sequentially set to various position values 202. A contrast value of the image (i.e. sensed by image sensor 106) is taken at each position value 202 and a curve fitting algorithm is applied (i.e. within ISP 112) to determine curve fitting line 204. Peak 206 of curve fitting line 204 is then selected for the best focus position, whereby Driver circuit 110 controls AF VCM 108 to set lens 104 to a particular position. The time required to translate lens 104 to a series of position values 202 is inefficient.